Hi,
 
I'm trying to learn how to use FuncAnimation. I made some small modifications to one of the matplotlib examples & tried it out, but I encounter a problem. I'm trying to update a line plot every 1 sec & I have my x-axis limit set to (0,10) initially. When the plot reaches x=10, I change the x-axis limit to (10,20) & continue the plot from there. I found that the 1st 2 seconds of the plot is always re-drawn in the 10th to 12th seconds, 20th to 22nd seconds and so on. I don't understand what's going on, so I hope someone here in this list can help me.
 
Just in case you don't understand what I mean, I've included the code below so you'll have a better idea when you run the code:
 
import matplotlib
import numpy as np
from matplotlib.lines import Line2D
import matplotlib.pyplot as plt
import matplotlib.animation as animation
class Scope:
    def __init__(self, ax, maxt=10, dt=1):
        self.ax = ax
        self.dt = dt
        self.maxt = maxt
        self.tdata = [0]
        self.ydata = [0]
        self.line = Line2D(self.tdata, self.ydata, marker='o')
        self.ax.add_line(self.line)
        self.ax.set_ylim(0, 200)
        self.ax.set_xlim(0, self.maxt)
        self.ax.set_xlabel("Time(s)")
        self.ax.set_ylabel("Jitter Buffer Size(ms)", color=self.line.get_color())
#        self.ax.yaxis.label.set_color(self.line.get_color())
    def update(self, y):
        lastt = self.tdata[-1]
        if lastt == self.tdata[0] + self.maxt: # reset the arrays
            self.tdata = [self.tdata[-1]]
            self.ydata = [self.ydata[-1]]
            self.ax.set_xlim(self.tdata[0], self.tdata[0] + self.maxt)
            self.ax.figure.canvas.draw()
        t = self.tdata[-1] + self.dt
        self.tdata.append(t)
        self.ydata.append(y)
        self.line.set_data(self.tdata, self.ydata)
        return self.line,

def emitter():
    while True:
        yield np.random.randint(0,200)
fig = plt.figure()
ax = fig.add_subplot(111)
scope = Scope(ax)
# pass a generator in "emitter" to produce data for the update func
ani = animation.FuncAnimation(fig, scope.update, emitter, interval=1000,
    blit=True)

plt.show()
Best Regards,
Clare.